Floodplain Information Report: Crystal River

I I I FLOODPLAIN INFORMATION REPORT I CRYSTAL RlVEI TOWN OF MARBLE VICINITY I GUNN I SON COUNTY COLORAOO I I r v y J I I Jty I I I I I Prpj arpd for Prl par j hy I Ikparlml lll of ICON EIlilll prillJlle Nal url Rt SOllH S 100 S kroll Strl pI I Colorado W tN ui II ltX Consryat ion Board CI ulpllllial Colorado 0112 I I n ShPrmall Slrl I t R xKI1 nl m 1 221 0802 IlJpllu r Color do 8020 I J C QiN ENGINEERING INC I August 200 I I I I TABLE OF CONTENTS Page I 1 0 INTRODUCTION L1 Purpose of Study I 1 2 Authority and Acknowledgements I I 1 3 Coordination I 1 4 Previous Studies 3 I 2 0 AREA STUDIED 21 Scope of Study 3 2 2 Community Description 3 I 23 Watershed Description 4 24 Flooding History 5 I 3 0 ENGINEERING METHODS 31 Hydrologic Analyses 7 3 2 Hydraulic Analysis 7 I 4 0 FLOODPLAIN MANAGEMENT APPLICATIONS 41 Floodplain Boundaries 8 I 4 2 Floodways 8 5 0 LOCATION OF DATA 9 I 6 0 BIBLIOGRAPHY AND REFERENCES 10 TABLES I Table I Crystal River Vicinity Climatology Data 4 Table 2 Historic Floods Crystal River 5 I Table 3 Summary ofDischarges for the Crystal River 7 FIGURES I Figures 1 2 Photos 1945 Flood Event Marble Colorado 6 Figure 3 Floodway Schematic 9 I PLATES Plate I Vicinity Map 2 Plates 2 3 Floodway Data Tables I Plate 4 Plate Index Map Plates 5 12 Flood Hazard Area Maps Plates 13 22 Flood Profiles I Plate 23 Typical Cross Sections I Cover Photo Snowshoe Ranch Bridge over the Crystal River Brian LeDoux September 2003 I I I 1 0 INTRODUCTION 1 1 Purpose of Study I This Floodplain Information Report provides new and revised information on the existence and severity of flood hazards along the Crystal River in the geographic area of the Town of Marble and in unincorporated portions of I Gunnison County Colorado Plate I This study has developed flood risk data that will be used to assist the County and the Town of Marble in its efforts to promote sound land use management and regulation of floodplain I development This report may also be used by FEMA as an existing data study XDS for future Flood Insurance Study revisions I 1 2 Authority and Acknowledgments The source of authority for this Floodplain Information Report is the Colorado I Water Conservation Board under Contract Numbers CI53924 and CI53986 with ICON Engineering Inc to perform hydrologic and hydraulic analysis to complete a floodplain delineation study on the Crystal River within Gunnison I County Colorado According to Section 37 60 106 1 c of the Colorado Revised Statutes the Colorado Water Conservation Board has the power and duty to devise and formulate methods means and plans for bringing about I the greater utilization of the waters of the state and the prevention of flood damages therefrom I 13 Coordination During the preparation of this Floodplain Information Report for Gunnison County and the Town of Marble the following public and private entities were I contacted and were instrumental in the preparation of this report Colorado Water Conservation Board CWCB Gunnison County Town of Carbondale U S Geological Survey USGS Marble Historical Society and Museum I ICON Engineering Inc and Kucera International Inc Specifically the CWCB USGS and Gunnison County supplied information used in the I preparation ofthis report A general historical information search was coordinated with the Marble Historical Society and Museum for historical background information I available publications and photographs of past floods Much of the information presented in this study was obtained from the Town of Marble I website Reference I The USGS was contacted to obtain historic stream gage data Additionally the flood frequency analysis program PEAKFQ Reference 2 was obtained from I the USGS and used for developing flood discharges for this study The Gunnison County Planning Department provided mapping of the I Crystal River study reach Reference 3 ICON Engineering Inc I I August 2004 I I I CRYSTAL RIVER STUDY LIMIT MAP I 10 DENVER us INlERSTATE 70 I I TO GRANO JINCllON I 1b EAGLE COUNTY GARFiELD COUNT I CiRBONOAl 1 I Iv 1 8 I I I I I DELTA vC U 1 jd I I I vis C U N I GU NNi V I I PLATE 1 I I ICON Engineering Inc 2 I August 2004 I I I Supplemental background information and assistance in project coordination was supplied by the CWCB I 14 Previous Studies One detailed floodplain study was previously completed for the Crystal River I in the vicinity of the Town of Marble Colorado In 1979 Wright Water Engineers under contract to Pitkin County and the Colorado Water Conservation Board completed a report entitled Floodplain Information I Report Crystal River and Coal Creek Pitkin County Colorado Reference 4 This report included detailed hydrologic and hydraulic analyses for the Crystal River in Pitkin County The upstream limit of the 1979 study is approximately I six miles downstream of the Town of Marble and approximately three miles downstream ofthe downstream limit of this study at the County Road 3 bridge I A Flood Hazard Boundary Map FHBM dated June 17 1977 was previously developed for the Town of Marble and Gunnison County by the U S Department of Housing and Urban Development Federal Insurance I Administration Reference 5 I 2 0 AREA STUDIED 2 1 Scope ofStudy I This Floodplain Information Report covers a reach of the Crystal River within the Town of Marble and portions of unincorporated Gunnison County Colorado For this report the Crystal River has been studied using detailed I methods for a reach of approximately 45 miles in length The study reach extends from just downstream of the Gunnison County Road 3 bridge to of the Beaver Lake State Area I upstream Fishing 2 2 Community Description Gunnison County is located in central western Colorado approximately 130 I miles south of the Colorado Wyoming state line The Town of Marble is located in northwestern Gunnison County The Town of Marble was founded in 1881 by settlers and prospectors and was officially incorporated in 1899 I The peak population of Marble occurred from 1912 to 1917 when the town supported a population of around 1 400 people Currently the population of Marble is around 300 people One of the world s largest concentrations of I marble is located in the mountains immediately to the south of the Town which was the source of the town s name and growing economy in the early I 1900 s I ICON Engineering Inc 3 I August 2004 I I I 2 3 Watershed Description The Crystal River watershed is within the Colorado River Basin and extends I high into the Elk Mountain Range in the Rocky Mountains The watershed also encompasses area from the White River National Forest and Maroon Bells Snowmass Wilderness The elevation ofthe watershed approaches 14 200 feet I at the top of Maroon Peak located within the famous mountain group the Maroon Bells The watershed elevation drops to around 6 100 feet where the Crystal River discharges into the Roaring Fork River near Carbondale I Colorado The Crystal River mainstem is approximately 30 miles long extending from I the Town of Crystal located approximately 5 miles upstream of Marble to the Town of Carbondale The channel gradient is very steep with slopes ranging I from 3 8 near Crystal to 14 upstream of Carbondale Vegetation within the Crystal River watershed reflects a sparsely developed mountain climatology Between Marble and Carbondale the watershed is I densely vegetated with evergreen and aspen trees along with other natural mountain vegetation Above Marble and up to about 11 200 feet the watershed reflects a high alpine environment with woody vegetation along I with rock outcroppings Rock talus and steep mountains are prevalent above 11 200 feet I The Crystal River basin is a semiarid mountain environment with cool summers and long winters Runoff is attributed to intense localized thunderstorm rainfall events during the summer months and snow melt during I the spring and early summer months The following table provides climatological data for Aspen Colorado located approximately 20 miles northeast of Marble and for Crested Butte Colorado located approximately 41 I miles southeast of Marble Aspen and Crested Butte are the closest National Weather Service Station locations to Marble I Table Crystal River Vicinity Climatology Datal Mean Annual July Mean January Mean I LOCATION Precipitation Temperature Temperature Cinches CO F CO F I Aspen Colorado 23 3 617 20 7 Crested Butte Colorado 23 9 56 0 8A I 1971 IThis data was compiled from National Weather Service records from year to 2000 I ICON Engineering Inc 4 I August 2004 I I I 24 Flooding History The history of flooding in the vicinity of the Town of Marble and the Crystal I River has been best documented by the 1979 Floodplain Information Report for the Crystal River and Coal Creek prepared for Pitkin County by Wright Water Engineers Inc This report documents historic floods from interviews I with local residents and a Corps of Engineers hydrologic study on the Crystal River Reference 6 This report indicates that the largest flows recorded on the Crystal River occur as a result of snowmelt during the spring and early I summer months Flooding during the late summer and fall months results from rainstorms Often these storms will also initiate large mud debris flows on tributaries to the Crystal River Local residents recall that Highway 133 has I been closed many times by mud slides in the summer months The largest recorded snowmelt and rain floods in the Crystal River basin have been tabulated in Table 2 This table was compiled from data presented by the U S I Geological Survey Water Supply Records References 7 8 9 I Table 2 Historic Floods Crystal

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